Demo de utilização da Câmera - Xamarin.Forms http://julianocustodio.com/camera-xamarin-forms

MainActivityDemoCamera.cs

using Plugin.Media;
using Android.App;
using Android.Content.PM;
using Android.OS;

namespace DemoCamera.Droid
{
    [Activity(Label = "DemoCamera", Icon = "@drawable/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override async void OnCreate(Bundle bundle)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);

            await CrossMedia.Current.Initialize();

            global::Xamarin.Forms.Forms.Init(this, bundle);
            LoadApplication(new App());
        }
        
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Android.Content.PM.Permission[] grantResults)
        {
            Plugin.Permissions.PermissionsImplementation.Current.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }
}